Staminal Evolution In The Genus Salvia (Lamiaceae): Molecular PhylogeneticEvidence For Multiple Origins Of The Staminal LeverJay B. Walker & Kenneth J. Sytsma (Dept. of Botany, University of Wisconsin,Madison)Annals of Botany (in press)Abstract• Background and Aims - The genus Salvia has traditionally included any member of thetribe Mentheae (Lamiaceae) with only two stamens and with each stamen expressing anelongate connective. The recent demonstration of the non-monophyly of the genuspresents interesting implications for staminal evolution in the tribe Mentheae. In thecontext of a molecular phylogeny, we characterize the staminal morphology of thevarious lineages of Salvia and related genera and present an evolutionary interpretation ofstaminal variation within the tribe Mentheae.• Methods. Two molecular analyses are presented in order to investigate phylogeneticrelationships in the tribe Mentheae and the genus Salvia. The first presents a tribalsurvey of the Mentheae and the second concentrates on Salvia and related genera.Schematic sketches are presented for the staminal morphology of each major lineage ofSalvia and related genera.• Key Results. These analyses suggest an independent origin of the staminal elongateconnective on at least three different occasions within the tribe Mentheae, each time witha distinct morphology. Each independent origin of the lever mechanism shows a similarprogression of staminal change from slight elongation of the connective tissue separatingtwo fertile thecae to abortion of the posterior thecae and fusion of adjacent posteriorthecae. We characterize a monophyletic lineage within the Mentheae consisting of thegenera Lepechinia, Melissa, Salvia, Dorystaechas, Meriandra, Zhumeria, Perovskia, andRosmarinus.• Conclusions. Based on these results, we can demonstrate (1) the independent origin ofthe staminal lever mechanism on at least three different occasions in Salvia, (2) Salvia isclearly polyphyletic, with five other genera intercalated within Salvia, and (3) staminalevolution has proceeded in different ways in each of the three lineages of Salvia but hasresulted in remarkably similar staminal morphologies.Key words – staminal morphology, Salvia, Mentheae, Dorystaechas, Meriandra,Perovskia, Rosmarinus, Zhumeria, Lepechinia, Melissa, key innovation, floral evolution.Staminal evolution in Salvia p. 2The genus Salvia (Lamiaceae: tribe Mentheae) represents a cosmopolitan assemblageof nearly 1000 species displaying a remarkable range of variation in growth form,secondary compounds, floral form, and pollination biology. Salvia has radiatedextensively in three regions of the world: Central and South America (500 spp.), WesternAsia (200 spp.), and Eastern Asia (100 spp.). Each of these radiations displays theunusual morphological character which has led to the long standing assumption that Salviais monophyletic: the significant elongation of the connective tissue of the two expressedanthers (Fig. 2). The demonstration of the non-monophyly of the genus (Walker et al.,2004) has led to a reinvestigation of the staminal morphology within Salvia and closelyrelated genera in the Mentheae. This paper presents a molecular phylogeny of Salvia andrelated genera, characterizes the staminal morphology in the various lineages of the genusSalvia and closely related genera, and interprets that staminal morphology in aphylogenetic context.Salvia is distinguished from the other 72 genera in the tribe Mentheae by having thetwo posterior stamens aborted, and the connective separating the thecae of the twoexpressed stamens significantly elongated (Fig. 2). It is the elongation of the staminalconnective that enables the formation of the lever mechanism of pollination for whichSalvia is best known (Fig. 1) (see Claßen-Bockhoff et al. 2003; 2004a for thoroughreviews). The significant species radiations that are correlated with the presence of thelever mechanism in Salvia suggest it is the lever mechanism in a selective regime ofpollination that is driving evolution in the group (Claßen-Bockhoff et al., 2004b). Thesignificance of this lever mechanism to the reproductive biology in Salvia, first describedby Sprengel (1793), has received considerable attention (Muller, 1873; Zalewska, 1928;Hruby, 1934; Werth, 1956; Baikova, 2002; 2004; Claßen-Bockhoff et al., 2003; 2004a;Wester and Claßen-Bockhoff, 2005). Himmelbaur and Stibal (1932-1934) directlyaddressed staminal evolution in Salvia, presenting a hypothesis of parallel evolution ofthe lever mechanism (from a common ancestor) in the New World and the Old World.We present here the first, robust, Salvia-wide molecular phylogeny with sampling acrossthe tribe Mentheae to directly evaluate Himmelbaur and Stibal’s (1932-1934) hypothesis.Additionally, the following questions are addressed and answered: How many times hasan elongate connective originated in Salvia and related genera? How many times has thestaminal lever mechanism originated in Mentheae? What are the most closely relatedgenera to Salvia? What are the trends in staminal evolution within Salvia?The results will support independent origins of the staminal lever mechanism on atleast three different occasions. From a common ancestor, we document remarkablysimilar - yet independent - progressions in staminal evolution, each presumably underpollinator selection, and each arriving at strikingly similar functional endpoints in astaminal lever.MATERIALS AND METHODSTaxa samplingNomenclature for Salvia follows that suggested by Alziar (1988–1993). 144 trnL-Fsequences, 139 nuclear rDNA ITS sequences and 85 psbA-trnH sequences representingStaminal evolution in Salvia p. 338 genera and 144 species were obtained in this project (Table 1). Accessions, vouchers,locality and GenBank numbers are available in Table 1. The data matrix for the“Mentheae-wide analysis” combined ITS, psbA-trnH and trnL-F and consisted of 84taxa. The data matrix for the “Salvia clade analysis” combined ITS, and trnL-F andconsisted of 93 taxa. Outgroups chosen for the Mentheae-wide analysis were Ocimumbasilicum and Hyptis alata, both from the tribe Ocimeae. Within the Mentheae, 34genera were sampled that represented every subtribe within the Mentheae. Within the“Salvia clade analysis”, sampling concentrated on the genus Salvia (82 species sampled)and all genera indicated by the “Mentheae wide analysis” to be closely related to Salvia.Horminum pyrenaicum was
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